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Atmospheric methane concentrations are rising faster since 2007.
An international group of researchers led by LSCE (CEA-CNRS-UVSQ) has published a
thorough budget of methane sources and sinks1 over the last decade in the Earth
System Science Data (ESSD) journal, complemented by en editorial in Environmental
Research Letters, both to be published on December 12 2016. These studies show
that none of the scenarios of the 5th IPCC2 report correspond to the observed
increase in methane concentrations. The published results highlight the
contribution of methane on the climate change.
Methane is the third anthropogenic greenhouse gas after carbon dioxide (CO2) and water
vapor.
After a period of stabilization in the early 2000s, methane concentrations are rising again
since 2007, and faster than at any time in the past two decades since 2014.
The methane budget published in ESSD shows that:
• Natural emissions: Adding-up the individual estimates of all natural sources of
methane using process-based approaches leads to much larger total emissions than
expected from atmospheric observations.
• Anthropogenic emissions (excluding fossil fuel emissions) represent about 60% of
total methane emissions, more than a third of which (36%) come from agriculture (rice
cultivation and livestock) and waste management.
• Fossil related emissions: Emissions of methane produced more than 50,000 years
ago, could represent about 30% of total methane emissions, tough this is still the
subject of debate. Among them, 9% are natural (geological seepages) and 21% are
anthropogenic (coal, oil and gas production and use).
Changes in methane sources still not well known
The reasons for the changes in methane concentrations and its rapid increase since 2007
are still unexplained. The rise in global methane concentrations is most likely of biogenic
origin, probably from agriculture. However, a potential contribution from fossil fuel
production and use cannot be ruled out.
Discrepancies with the scenarios from the last IPCC1 report
None of the climate scenarios proposed in the last IPCC report properly reflects the actual
methane concentration and its increase in the atmosphere: three are too optimistic and the
last one is too pessimistic.
Towards a global methane budget
This study (ESSD article) presents existing knowledge on each single source of methane
from the largest (wetlands) to the smallest (hydrates) thanks to the collaboration of more
than 70 international researchers, who have specific expertise on the different methane
sources or sinks.
The lead authors also warn “we must continue to update the methane budget regularly, as
is the case for CO2. Methane has a shorter lifetime than carbon dioxide. Therefore, methane
mitigation offers rapid climate benefits as well as economic, health and agricultural
advantages that are highly complementary to CO2 reduction… and necessary to keep the
temperature change below 2 degree Celsius.“
Image copyright: Global Carbon Project
The study was led by Laboratoire des Sciences du Climat et de l’Environnement (LSCE – CEACNRS-UVSQ, France) as part of the Global Carbon Project. The data will be published on the
Global carbon Atlas: www.globalcaronatlas.org
sinks: chemical destruction in the atmosphere and soil uptake
Intergovernmental Panel on Climate Change
3 Representative Concentration Pathways corresponding to 8.5 Wm-2 additional radiative
forcing and about +4°C temperature increase in 2100 – RCP8.5
1
2
References
The Global Methane Budget 200-2012, Saunois et al., Earth System Science Data, 8, 1-55,
December 12 2016
The growing role of methane in anthropogenic climate change, Saunois M., Jackson R.,
Bousquet P., Poulter B. and Canadell J. G., Environnemental Research Letters, December 12
2016
About the Global Carbon Project and the Global carbon Atlas
The Global Carbon Project aims to assist the international scientific community to
collaborate on the carbon budget through a partnership between the International
Geosphere-Biosphere Programme and Future Earth. It produces an annual report on the
data regarding the carbon sources and sinks linked to human activity and how they affect
the environment. Each year, the data set is made available through the Global carbon Atlas
with the support of Fondation BNP Paribas. Available in five languages (English, French,
Spanish, Chinese and Russian) at www. Globalcarbonatlas.org.
Press Contacts
CEA – François Legrand [email protected] T : + 33 6 77 38 57 97
CNRS – Priscilla Dacher [email protected] T : + 33 1 44 96 46 06
Université de Versailles Saint-Quentin-en-Yvelines – Annelise Gounon-Pesquet [email protected]
T : + 33 1 39 25 41 75